Does your Garmin cadence sensor eat batteries like a Belgian eats frites?

[FastforaSlowGuy]

I've had my Garmin 500 for a couple years, but only recently broke down and got the speed/cadence sensor. The sensor works beautifully...for about 5 rides. The outage is clearly due to the battery, but I'm baffled why it would burn through batteries so quickly. Anyone else have this happen? I couldn't find any battery life data on Garmin's site.